The New York based Human Rights Watch[3] (HRW) condemned the video in a strongly worded report, in which they identify the rebel as Abu Sakkar, leader of a Homs-based militia, and call on the International Criminal Court (ICC) to investigate reports of atrocities committed in Syria.

The video, which can't be independently verified, shows a man apparently cutting out the liver and and heart from a corpse, before putting the heart in his mouth.

"I swear to God we will eat your hearts and your livers, you soldiers of Bashar the dog," the man says, standing over the corpse.

Human Rights Watch identified the man as the commander of the Independent Omar al-Farouq Brigade in tthe report released on Tuesday.

"The mutilation of the bodies of enemies is a war crime. But the even more serious issue is the very rapid descent into sectarian rhetoric and violence," HRW's Peter Bouckaert told Reuters news agency.

“One important way to stop Syria’s daily horrors, from beheadings to mutilations to executions, is to strip all sides from their sense of impunity,” said Nadim Houry, Middle East deputy director at Human Rights Watch. “These atrocities are shocking but so is the obstruction of some Security Council members that still do not support an ICC referral for all sides.”

The video emerged as Russia and the US appear to have pushed back the timeline for peace talkds on Syria. There has been a flurry of diplomacy in recent days, with UK, US and Russia meeting in a bid to bring the 2 year-old conflict to an end.